Cloning And Sequence Analysis Of Banana Vnd1 Transcription Factor And Its Overexpression In Transgenic Banana Plants
Vascular related NAC (NAM, ATAF and CUC) domain-containing genes are plant specific transcription factors
involved in regulation of tracheary element formation. Tracheary elements are elongated cells of xylem tissue characterized
by thick secondary wall formation and functions in transport of water. Banana VND1 is a transcription factor isolated by
PCR amplification from corm tissue of banana cultivar Rasthali and cloned in T- cloning vector for sequencing the amplified
PCR product. Sequence analysis indicated that banana VND1 is a homologue of Arabidopsis VND1 and contains the highly
conserved NAC domain. Banana VND1 was further cloned in plant specific cloning vector pCAMBIA1301 under the control
of maize polyubiquitin promoter, pZmUbi. The cloning was confirmed by colony PCR and subsequent sequencing of the
recombinant vector. Transgenic banana plants overexpressing banana VND1 were generated by Agrobacterium mediated
genetic transformation of banana cultivar Rasthali embryogenic cells. Transgenic nature of the shoots were confirmed by
genomic DNA PCR, Southern blot analysis and real time RT-PCR analysis. Transgenic plants displayed transdifferentiation
of leaf epidermal cells into tracheary element-like cells with ectopic deposition of secondary wall. Further, transient
overexpression of banana VND1 resulted in differentiation of banana embryogenic cells into tracheary element-like cells.
These results indicated the role of banana VND1 transcription factor in regulating tracheary element development in banana.